a control experiment buried fermented and buried non-fermented

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A Control ExperimentBuried Fermented and Buried Non-Fermented Food Waste

Soil Interactions

August 2009

Lawrence R. Green MD PhD


Contents:

What happens to food waste just buried in the soil?........................................................... 3Study Purpose: .................................................................................................................... 3Findings: ............................................................................................................................. 3

Buried Food Waste: ................................................................................................ 3Buried Bokashi Fermented Food Waste: ................................................................ 4

Experiments and Images:.................................................................................................... 4Photo-images of Buried Food recovered after 8 weeks: ......................................... 4Bokashi Fermented Food Waste: ............................................................................ 8Photo-images of recovered fermented food waste at 7 days: ................................. 8Photo-images of recovered fermented food waste at 14 days: ............................. 12Photo-images of recovered fermented food waste at 27 days: ............................. 13

Conclusions:...................................................................................................................... 14


What happens to food waste just buried in the soil?It is a perfectly reasonable question. One wonders does it make a difference to pre-treatthe food waste with microbes before it is placed in the ground. It is easy to run thecontrol experiment and as is evident in the images and measurements shown there is aprofound difference in the rate of food waste degradation related to how the waste istreated before it goes into the ground.

Study Purpose:There were two objectives in this semi-quantitative study. The first was to show thedifferences one can expect to see in the degrading processes when food waste is justburied in soil and left to degrade as opposed to bokashi fermenting food waste beforeburying it in the soil.

We want to show that it is possible to use a large plantar box filled with soil to degradefermented food waste efficiently. It is not known how much soil is needed to rapidlydegrade a fermented sample of waste material in a period of about 2 weeks.

In this experiment a volume of soil 5 times greater than the beginning load of fermentedfood waste was tested to determine if that was a sufficient amount of soil to completelywithin the month decompose the wasted material. Experience has shown that an averagecouple generating food waste will in a month produce approximately 1 cubic foot offermented waste material.

If this can be done, then it is then possible for high-rise or condominium dwellers to usethe bokashi fermentation system at home providing they use a plantar box on the balconyor roof to process food waste that is at least 5 times the volume of food waste that will begenerated each month.

Findings:

Buried Food Waste:

Food waste that is buried in the ground without a pre-treatment remains in the groundattracting flies and animals and does not rapidly degrade. A strong odor of rotting wastematerial is apparent as one approaches the burial site and it is more evident as onedisturbs the soil where waste had been buried. Approximately 90 % of the buried foodwaste is recovered even at 8 weeks after it had been buried.


Buried Bokashi Fermented Food Waste:

Food waste pretreated by bokashi fermenting and buried in soil in a garden container witha 5:1 volume soil to fermented food waste material rapidly degrades. There are no fliesor vermin attracted to the site. There is no apparent rotting odor even when the burial siteis disturbed. Most of the fermented food waste (estimated at 90% of the initial volume)is transformed into nutrient rich soil within 7 days from the time it is placed in the soil inthe garden container. Woody (grape stems, etc.) and bony materials take longer todegrade but appear well on the way even at 7 days. Grape stems and larger bones showevidence of decomposition at 3 weeks and are the only residuals recovered at the end ofthe month.

Experiments and Images:Two different experiments were done. In both experiments the soil was taken from thesame area in the garden. Five gallons of collected food waste was buried in the soilmixing it and covering it then with soil to a depth of 8 inches. In one experiment the foodwaste was buried and then recovered after 8 weeks to determine how muchdecomposition had taken place.

In the second set of experiments food waste was fermented using the bokashifermentation process and then buried in soil that had been placed in a garden containerthat was opened for inspection weekly to determine how much degrading of material hadoccurred.

Photo-images of Buried Food recovered after 8 weeks:

The food waste material in the experiment involving no pretreatment was allowed toremain in the ground for 8 weeks before it was screened to see how much material wasdegraded.

Non-degraded food waste was recovered by digging up soil at the burial site and filteringall the soil from the site through a ½ x ½ inch mesh screen. All particles that could beidentified as food waste material were set aside and then collectively washed with waterto remove loose dirt. The material that had been in the soil 8 weeks was then placed inthe original container to measure the recovery volume. It could then be estimated basedon the volume recovered relative to the volume that had been buried how efficiently thedegrading process was for buried food waste.

It was apparent (images as shown below) that food waste that was not fermented changedvery little during the 8 week period it was in the soil. A strong odor of decaying foodwaste was evident when the soil was disturbed and there were many insects and flies nearthe surface where the food waste had been buried.

Virtually all of the non-fermented food waste was easily recovered. The photo imagesshow bright red raw tomatoes and vegetable matter in the recovered material. Meatproducts were also easily identified. Measurements of the washed material recovered


from the soil reveal a volume recovery of approximately 90%. Decomposition was hardlydetectable. The strong odor of rotting food waste was very evident. These findings areshown in the photo images.

Photo Images of Non-fermented Food Waste RecoveredAfter 8 Weeks in the Soil

Food waste Recovery after 8 week burialNon-fermented food waste buried 1 foot in soil and examinedeach week for 8 weeks recovered by filtering through1/2 x 1/2 mesh wire screenInitial volume = 5 gallons

Food waste Recovery after 8 week burialrocks and food waste retained


Food waste Recovery after 8 week burialrocks and food waste retained on mesh screenready for wash down

Food waste Recovery after 8 week burialFood waste still evident with little decompositioneven after 8 weeks in the soil

Note there are abundant raw vegetable and meat particles observed even after the wastematerial had been in the soil for 8 weeks.


Food waste Recovery after 8 week burialClose up reveals raw vegetables, meat productsand peelings hardly degraded mixed with soil

Food waste Recovery after 8 week burialContents of non-degraded food waste from recoveryplaced in fermenting chamber with wheat branbokashi culture mix


Bokashi Fermented Food Waste:

In the second set of experiments the same volume of food waste (5 gallons) was allowedto first ferment using bokashi culture mix (www.bokashicycle.com). Fermenting of foodwaste was done for at least 7 days in the closed fermenter before it was placed in the soil.

A 25 cubic foot garden container was filled with screened soil as shown in the imagecollection. A 5 gallon (1 cubic foot) container of fermented food waste was then mixedwith the soil and covered with at least 8 inches of soil over the top of the fermented foodwaste and it was then allowed to remain undisturbed for a period of 1 week (July 21 toJuly 28, 2009).

The contents of the garden container were then transferred to a wheel barrow and withcareful screening using the ½ x ½ mesh wire screen residual material was collected andwashed so it could be identified and measured accurately.

Screen filtered soil was added to a garden container (shown below) that hadapproximately 4 inches of soil at the bottom. The volume of soil relative to the volumeof added food waste was 5:1.

The 5 gallon fermented food waste material was added to the container and more soil wasmixed into it before filling to the top of the container. Fermented food waste wasallowed to stand undisturbed for 7 days. After 7 days all of the soil in the container wasremoved and filtered to identify any residual non-degraded food waste. Retained foodwaste was sorted, washed and then photographed to get an accurate estimate of amount offermented food waste that had not degraded at 7 days.

Photo-images of recovered fermented food waste at 7 days:

As can be seen, most of the food waste (estimated at 90%) has already been converted tonutrient rich soil within the week in which it was buried. The waste that was retainedwas generally speaking bones, pits, and woody grape stems. A few badly discolored andshredded leaves, a grape and a jalapeno pepper were at 7 days not completely degraded(image as shown)..

These residual non-degraded at 7 day items in the fermented food waste were suspendedin the soil to give it more time to degrade.


25 cubic foot capacity gardencontainer

Screened soil prepared beforefilling garden container


Screened soil placed in gardencontainer to be mixed with fermentedfood waste following bokashifermentation

Fermented food waste in bottomof garden container


Buried fermented food waste insoil July 21, 2009

Soil with buried food waste takenout of garden container onJuly 28, 2009 and screened forresidual food waste


Most of food waste is convertedto soil at 7 days. A few bones, woodygrape stems, and pits and egg shellfragments and shredded banana plantleaf partially degraded evident afterscreening soil.


All of the recovered fermented food waste obtained at 7 days was suspended in the samesoil taken from the container to be opened, screened and photographed at 14 days . Afew shredded banana plant leaves, grape stems and bones were found but all otherfermented food waste was indistinguishable from soil by day 14.

Waste recovered at 2 weeks -Woody materials and bonefragments.

Shredded Banana treeleaf remnants

Bones recovered at2 weeks

Grape stemsdegrading



All of the recovered material at 14 days was placed back into the container with the samesoil and allowed to further decompose. The contents of the container were examined at27 days from the time of burial. Only the larger bones and a half dozen grape stems wereidentified. The bones were discolored and showed evidence of decomposition as shownin the photographs below.

Soil recovery at 27 daysfrom 25 cu ft plantar boxwith a few bones and grapestems residual screened

Soil recovery at 27 daysfrom 25 cu ft plantar boxwith a few bones and grapestems residual placed backin the box


Six grape stems partiallydecomposed and largerbones in process ofdecomposition

Magnification showingapparent fungal organismsinvading bony cortex

Conclusions:Food waste simply buried in the ground will not rapidly degrade and remains virtuallyunchanged for weeks. A foul rotting smell is easily detected in the vicinity of buriedfood waste; flies are evident and animals dig in the soil where the waste is buried. Itappears that 90% of the food waste can be recovered even at 8 weeks after burial.

Bokashi fermented food waste buried at the same depth in a garden container with a soilto waste volume of 5:1 rapidly transforms into a rich nutrient soil. No earth worms werepresent in the soil used to degrade the fermented food waste in this experiment.


No flies or foul rotting smells were observed in the attempt to recover buried wastematerial. It appears that woody and bony items require more than 7 days to completelydegrade.

More than 90% of the buried fermented food waste was degraded within 7 days afterbeing placed in the soil. Only woody (grape stems, etc.) and larger bones are recoveredafter 2 weeks and they appeared discolored and well into the degrading process.

With a larger planter box on the balcony or roof top, the food waste could be buried inthe soil with the expectation that it will be properly and rapidly converted to nutrient richsoil that could then be used to support and feed plants in other planter boxes.

Normally fermented food waste would be buried once every 4 – 5 weeks which appearsbased on these findings to be sufficiently adequate time for a transformation of waste tosoil that is rich in organic nutrients and microbes..

a control experiment buried fermented and buried non-fermented

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